setExcludedPackages

Specify Java packages that should be excluded from this mapping.
Any classes in such a package (or any of its subpackages) will be
ignored by this HandlerMapping.

Default is to exclude the entire "org.springframework.web.servlet.mvc"
package, including its subpackages, since none of Spring's out-of-the-box
Controller implementations is a reasonable candidate for this mapping strategy.
Such controllers are typically handled by a separate HandlerMapping,
e.g. a BeanNameUrlHandlerMapping,
alongside this ControllerClassNameHandlerMapping for application controllers.